The present invention relates to a data transmission and receiving apparatus and method for sending and receiving data recorded to a recording medium such as an optical disc or magnetic tape by way of a digital interface.
The IEEE 1394 system has attracted attention recently as a serial transmission method for digital data. Not only can the IEEE 1394 system be used in place of the conventional SCSI standard for computer data transmissions, it can also be used for transmitting AV data. This is because two communications methods are defined in the IEEE 1394 system: asynchronous communication and isochronous communication. Isochronous communication is a data transmission method that can be used for transmitting data requiring real-time performance such as AV data. In isochronous communication the bandwidth required for data transmission is obtained before transmission starts. Data is then transmitted using that bandwidth. The real-time characteristic of the data transmission is thereby assured. Asynchronous communication, on the other hand, is a transmission method used for transmitting data that does not require real-time performance, such as transmitting computer data. This can be thought of as equivalent to transmission methods such as the conventional SCSI transmission method.
Various methods have been proposed as high level transmission protocols under the IEEE 1394 system, and one of these can be referred to as the AV protocol. The AV protocol is being standardized as IEC 61883, which defines sending and receiving AV data requiring real-time performance using isochronous communication, and sending and receiving control commands asserted to devices using asynchronous communication.
The AV/C command set is one of the above-noted control command systems. Control commands for VCRs, for example, are defined in the AV/C command set. A method for expressing information stored by the device (such as the device state and recording medium descriptor) using a list structure is also defined in the AV/C command set.
As an example of the prior art, this method is described below with reference to FIG. 13.
FIG. 13 is a schematic diagram showing an example of the list structure defined by the AV/C command set. As shown in the figure, list A 2001 consists of a list header 2002 and zero or more (N shown in the figure) objects 2003. Information relating to list A 2001 overall is written to the list header 2002. The objects 2003 are equivalent, for example, to a unit such as an audio track recorded to a disk; a descriptor relating to each audio track, for example, is written to an object 2003. In addition, a structure with the same concept as the directory of a computer file system can also be used as an object, and can be used to express a list having a hierarchical structure. In FIG. 13 object #3 of list A 2001 is shown as an object indicating a directory, in this example having a list B 2101 as a list for a level under object #3 in list A 2001. This list B 2101 has a list header 2102 and objects 2103 similarly to list A 2001.
These lists are generated inside the device, and can be accessed by an external device by way of IEEE 1394 so that the external device can obtain the information stored by the other device.
When an object contains a descriptor for AV data, for example, AV data recorded to a recording medium can be reproduced by specifying the object ID and sending a play command, for example, to the device. Moreover, if a list is specified and a play command is sent to the device, AV data is reproduced in the order written in the list.
A variety of information can be written using this list structure. For example, devices that use AV discs can write the content recorded to the disc, and the sequence for program playback. The sequence for program playback can also be specified from an external device by accessing the list describing the program playback sequence from an external device.
An example of a title or text file access sequence in a conventional data transmission and receiving apparatus is described below with reference to FIG. 14.
FIG. 14 shows a list structure for a case in which the list shown in FIG. 13 is applied to an optical disc to is recorded an audio track, audio title, or text, for example. FIG. 14 shows a typical content list 1301, audio list 1311, and title list 1351 structure. In this example audio data for two songs, song A and song B, is recorded to the optical disc. In the audio data descriptor, the title information is represented by title list 1351 separately from the content list 1301.
The content list 1301 is a list of the overall content recorded to the optical disc. The content list 1301 contains a first object 1303 and second object 1304. First object 1303 and second object 1304 are objects for presenting a directory; first object 1303 has audio list 1311, and second object 1304 has text file list 1331, as lists one level lower.
Audio list 1311 consists of list header 1312, first object 1313, and second object 1314. In this case, first object 1313 and second object 1314 correspond respectively to the descriptor for songs A and B (not the audio data itself). In addition, the list header 1312 comprises number of songs (number of objects) 1321. In this case the number of songs is two. The first object 1313 and second object 1314 respectively comprise the playback time 1322 and 1324 of each song, and a pointer 1323 and 1325 to each song title.
The text file list 1331 comprises list header 1332, first object 1333, second object 1334, and third object 1335, and stores a text file descriptor. A descriptor relating to a text file includes, for example, the content written to that text file (an identifier indicating a lyrics file or artist information file, for example), the file size, and file creation date and time. In this example the first object 1333 corresponds to a text file representing the entire optical disc, for example, a text file descriptor (not the text file data itself) such as the artist information when the disc records only audio data from a single artist. The second object 1334 and third object 1335 correspond respectively to a text file descriptor (not the text file data itself) for songs A and B. In this case these store a file descriptor relating to a lyrics file and artist information file.
Each object of title list 1351 records the title data itself. In this case it is assumed that a disc title representing the overall audio list is written to first object 1333, the title of song A is written to second object 1354, and the title of song B is written to third object 1355. Link information (an ID for second object 1354) to the second object 1354 of title list 1351 is written in the pointer 1323 to the title in the first object 1313, that is, the object indicating song A in the audio list 1311. Likewise, link information (an ID for the third object 1355) to the third object 1355 of title list 1351 is written in the pointer 1325 to the title in the second object 1314 that is the object indicating song B.
By thus using a list structure with a general format, an external device can access data stored by a data transmission and receiving apparatus by way of a digital interface without knowing the device-specific data storage structure.
For example, when an external device wants to access a disc title in a data transmission and receiving apparatus, it accesses title list 1351 and reads first object 1333. In this case, the first object in the title list is predefined as a disc title. In addition, to access the title of song A, it reads content list 1301, obtains the ID for the audio list, reads the audio list, obtains the pointer 1323 to the title of song A, and based on this accesses the second object 1334 of title list 1351. In this case, if the audio list object can be accessed, the method of accessing the corresponding title information is known mechanically. Furthermore, the second object in the text file list 1331 is accessed to access the text file descriptor corresponding to song A (the first object in the audio list). In this case, too, the second object of text file list 1331 is a descriptor for the text file corresponding to song A (the first object of the audio list) is predefined as the second object of the text file list 1331.
It is therefore possible to access a title or text file descriptor as described above.
(Technical problem to be resolved)
When accessing text files and text information that is attribute data of the AV data from an external device with the above described conventional method, the procedures for accessing text data and text files differ when accessing is by way of following links from an AV data descriptor, and access from an external device is difficult.
More specifically, in the case of a title there is a title information pointer in the AV data descriptor and the title is accessed by following the pointer, but a text file is accessed directly. Moreover, descriptors for individual pieces of song data are written from the first piece in an AV data file object, but with a text file object the first descriptor is for text relating to the entire disc, and the sequence in which descriptors are written is not uniform. As a result, the method of accessing a disc title not corresponding to the individual AV objects is also different from that for titles corresponding to individual AV objects.
Furthermore, with the above noted method, when an external device writes a new title or other information when accessing a text file or text information that is attribute data for AV data, the external device must determine the write location, and the process is complicated.
More specifically, because a title information pointer is in the AV data descriptor, a title can be accessed by following the pointer, but text files are accessed directly. Moreover, the write sequence for AV data file objects and text file objects is nonuniform, and the method of accessing a disc title not corresponding to an individual AV object is also different from a title corresponding to an individual AV object. As a result, a different location must be determined for each write, and the process becomes complicated.
Furthermore, with the above noted conventional method, when AV data is deleted, the external device must delete other objects linked from the object corresponding to the deleted AV data, and the process is complex.
Furthermore, with the above described conventional method, when AV data recorded to a recording medium is divided by a command from an external device, the external device must generate an object for the descriptor corresponding to the newly generated AV data, and the process is complex.
The above described conventional method thus has numerous problems.
The present invention resolves the aforementioned problems of the prior art, and has as an object to provide a data transmission and receiving apparatus and method that can unify the access procedure for text information and text files when accessing by following links from an AV data descriptor when accessing a text file or text information that is attribute data of the AV data from an external device.
A further object of the present invention is to provide a data transmission and receiving apparatus and method whereby it is not necessary for the external device to determine the write location when the external device newly writes title or other information when accessing a text file or text information that is attribute data of the AV data from the external device.
A further object of the present invention is to provide a data transmission and receiving apparatus and method whereby it is not necessary for the external device to delete another object linked from an object corresponding to deleted AV data when AV data is deleted.
A further object of the present invention is to provide a data transmission and receiving apparatus and method whereby it is not necessary for the external device to generate a descriptor object for newly generated AV data when AV data recorded to a recording medium is divided by a command from the external device.
(Method of resolving the problem)
To achieve the above object, the present invention, when mutually converting a list and first descriptor that is descriptor for a content block recorded to a recording medium, groups the first descriptor into a third descriptor expressed independently of the content block and a fourth descriptor other than the third descriptor; generates a first list indicating the fourth descriptor and a second list block indicating the third descriptor; writes a reference to the content block in the third descriptor to the list header of the second list block; and writes link information to a reference to the content block in the third descriptor to the list header of the first list.
As a result, the procedure for accessing a reference to the content block in the third descriptor can be made easy.
(Improvement over the prior art)
In this way, in a data transmission and receiving apparatus and method according to the present invention, a recording medium descriptor is expressed using a list structure when accessing by way of a digital interface a recording medium to which is recorded AV data or text data such as titles for the AV data. For the list structure, a list is generated for the AV data descriptor and text data descriptor, and a pointer to a list of related text data descriptor is written to the AV data list object. As a result, text information that is attribute data of the AV data can be accessed from an external device by following links from the AV data descriptor, and simplified access from an external device can be promoted.
Furthermore, a recording medium descriptor is expressed using a list structure with the present invention when accessing by way of an intervening digital interface a recording medium to which is recorded AV data, text data such as a title for the AV data, and a text file such as lyrics for the AV data. For the list structure, an individual list is generated for the AV data descriptor, text data, descriptor for the text file representing the AV data overall, and descriptor for other text files, and a pointer to a list of related text data and text file descriptors is written to the AV data list object. It is thus possible to access text files and text information that are attribute data of the AV data from an external device by following links from the AV data descriptor. In addition, because a descriptor for a text file representing all of the AV data is stored in a separate file, and the list storing a descriptor for the text information associated with the individual AV data and other text files is written with the same structure as the list in which an AV data descriptor is stored, text information and text files can be accessed from an external device using the same procedure, and access from an external device can be simplified.
Furthermore, with the present invention, a recording medium descriptor is expressed using a list structure when accessing by way of a digital interface a recording medium to which is recorded AV data, text data such as titles for the AV data, or a text file such as lyrics for the AV data. For the list structure, an individual list is generated for the AV data descriptor, text data, and a text file descriptor, and a pointer to a list of related text data and text file descriptors is written to the AV data list object. If text data corresponding to the AV data is not recorded to the recording medium at this time, the objects in the lists for the text data, etc., are left empty. As a result, text files and text information that are attribute data of the AV data can be accessed from an external device by following links from the AV data descriptor. In addition, because text information and text files are written using the same structure, text information and text files can be accessed from an external device using the same procedure, and access from an external device can be simplified. Furthermore, because empty objects are generated even if the title or other text information is not recorded to the recording medium at this time, the write location can be determined in advance when an external device newly writes a title or other information.
Furthermore, with the present invention, a recording medium descriptor is expressed with a list structure when accessing by way of a digital interface a recording medium to which is recorded AV data, text data such as titles for the AV data, or a text file such as lyrics for the AV data. For the list structure, an individual list is generated for the AV data descriptor, text data, and a text file descriptor, and a pointer to a list of related text data and text file descriptors is written to the AV data list object. Then, when AV data is deleted, the object(s) in the title list and object(s) in the text file linked from the object corresponding to the deleted AV data are deleted at the same time. As a result, text files and text information that are attribute data of the AV data can be accessed from an external device by following links from the AV data descriptor. In addition, because text information and text files are written using the same structure, text information and text files can be accessed from an external device using the same procedure, and access from an external device can be simplified. Furthermore, when AV data is deleted in this case, it is not necessary for the external device to delete a descriptor corresponding to the deleted AV data or descriptor (text information or text file) because objects in the title list and objects in the text files linked from the object corresponding to the deleted AV data are deleted at the same time, and uniform list management can be facilitated. In addition, content recorded to the recording medium can be immediately reflected in the list.
Furthermore, with the present invention, a recording medium descriptor is expressed using a list structure when accessing by way of a digital interface a recording medium to which is recorded AV data, text data such as titles for the AV data, or a text file such as lyrics for the AV data. For the list structure, an individual list is generated for the AV data descriptor, text data, and a text file descriptor, and a pointer to a list of related text data and text file descriptors is written to the AV data list object. Then, when AV data is divided, a descriptor for the text data and text file corresponding to the divided newly generated AV data is added to the text data and text file descriptor list as a new object. Then, link information to the newly generated text data and text file descriptor object is written to the object corresponding to the newly generated AV data. As a result, text files and text information that are attribute data of the AV data can be accessed from an external device by following links from the AV data descriptor. In addition, because text information and text files are written using the same structure, text information and text files can be accessed from an external device using the same procedure, and access from an external device can be simplified. Furthermore, when AV data is divided, an object in the title list and an object in the text file are generated for the divided newly generated AV data, and a link is made from the newly generated AV data object. Therefore, even when AV data recorded to a recording medium is divided by a command from an external device, it is not necessary for the external device to generate a descriptor for the newly generated AV data or objects corresponding to the descriptor (text information and text file), and uniform list management and simplified processing can be promoted.
Furthermore, with the present invention, a recording medium descriptor is expressed with a list structure when accessing by way of a digital interface a recording medium to which AV data and still image data, for example, are recorded. For the list structure, individual lists are generated for the descriptors of the AV data, still image data representing the disc, and other still image data. Furthermore, when a playback command specifying an AV data list is sent from an external device, playback starts from the AV data corresponding to the first object at the beginning of the AV data list. As a result, because data blocks not associated with AV data are managed using the same method described in the second embodiment for data associated with AV data, list structure uniformity can be promoted, and simplified access can be facilitated when this data or descriptor for this data is accessed from an external device. Furthermore, synchronized playback of AV data, data associated therewith, and data not associated therewith can be easily accomplished because the list formats are the same.